1. Field of the Invention
The present invention relates to a plasma display panel (PDP), and more particularly, to a plasma display panel with an auxiliary bonding pad.
2. Description of the Prior Art
With the progressive development of the electronics industry, the demand for flat panel displays (FPD) has been increased. The plasma display panel (PDP) has the greatest market potential amongst all FPDs. In the manufacturing process of a PDP, a front substrate is sealed with a rear substrate to form lots of discharge cells therebetween. A plurality of printed circuit boards(PCBs) are then connected with the front substrate or the rear substrate for controlling these discharge cells. The printed circuit boards are used to connect with other electrical devices, so the quality of the PDP will be affected by the reliability and the bonding strength between the printed circuit boards and the front substrate (or the rear substrate).
Please refer to FIG. 1 and FIG. 2. FIG. 1 is a schematic diagram showing a bonding area 16 of a rear substrate 12 in a plasma display panel 10 according to the prior art.
FIG. 2 is a schematic diagram of a process for sealing the rear substrate 12 and a printed circuit board 22 in the prior art. As shown in FIG. 1, the plasma display panel 10 includes a front substrate (not shown) and a rear substrate 12 parallel to and spaced apart from the front substrate. A bonding area 16 is defined out of the area that the rear substrate 12 sealed with the front substrate. The bonding area 16 is connected to a printed circuit board 22. A plurality of bonding electrodes 14 is formed on the bonding area 16 and electrically connected with the printed circuit board 22. As shown in FIG. 2, a plurality of board electrodes 24 is formed on the printed circuit board. These board electrode 24 don""t connect to each other. Each board electrodes 24 is positioned corresponding to one of the bonding electrodes 14. An anisotropic conductive film(ACF) 26, having conductive particles, fills the space between the rear substrate 12 and the printed circuit board 22 so as to connect the rear substrate 12 with the printed circuit board 22 electrically and physically.
Please refer to FIG. 3. FIG. 3 is a schematic diagram of the sealing structure of the rear substrate 12 and the printed circuit board 22. At the final step of the sealing process, a layer of silicon paste 29 is coated between the rear substrate 12 and the printed circuit board 22. The silicon paste 29 is used to protect the ACF 26 from the air and to strengthen the connection between the rear substrate 12 and the printed circuit board 22. However, in the PDP 10 formed by the prior art method, a space 27 is usually formed between the ACF 26 and the front end of the bonding electrode 14, and therefore an inner silicon paste 291 fails to contact with the substrate 12 or the board electrodes 24. Thus, the inner silicon paste 291 fails to adhere the rear substrate 12 to the printed circuit board 22. Besides, after the silicon paste 29 is formed, the moisture may exist in the air of the space 27. This moisture will influence the bonding properties of the ACF 26 so that the ACF 26 may be peeled off from the bonding electrodes 14 or the board electrodes 24. Therefore, the bonding electrodes 14 and the board electrodes 24 may fail to remain electrically connected, or the moisture may reduce the bonding effect of the silicon paste 29, so the reliability of the PDP is affected.
It is therefore an object of the present invention to provide a plasma display panel (PDP) having an auxiliary bonding pad to solve the above-mentioned problems.
According to the present invention, a plasma display panel includes a substrate and a printed circuit board. The substrate has an edge, and a plurality of bonding electrodes are formed on the substrate along the edge of the substrate. Each bonding electrode neither overlaps with any of the other bonding electrodes nor electrically connects to any of the other bonding electrode. The bonding electrodes are spaced from the edge of the substrate by a distance. Further, a plurality of board electrodes is formed on the printed circuit board. Each board electrode neither overlaps nor connects to any of the other bonding electrode. The position of each board electrode corresponds to the position of a corresponding bonding electrode. Beside, an auxiliary bonding pad is formed between the bonding electrodes and the edge of the substrate. When a conductive adhesive layer and a protective adhesive layer are formed to adhere the substrate with the printed circuit board, the auxiliary bonding pad can reduce a space formed between the bonding electrodes and the conductive adhesive layer, and also eliminates the possibility of the bubble formation therebetween. Therefore, the substrate is completely sealed with the printed circuit board.